Zn-doped BiOCl materials with gradient defect interfaces and their catalytic applications

Abstract

Zn-doped BiOCl materials with gradient defect interfaces and their catalytic applications belong to the field of catalysis. This involves using Zn, which has a smaller ionic radius... 2+ Partially replaces Bi 3+ Inducing lattice distortion, Zn was simultaneously constructed in BiOCl. 2+ Doping site --- Oxygen vacancy --- Elemental Bismuth (Bi) 0 "Gradient defect interface, and oxygen vacancy concentration varies with Zn." 2+ The doping concentration increases, enhancing the absorption capacity. This interface collectively regulates the band structure, significantly enhancing visible light absorption. Under the coupling effect of the illumination field and the built-in polarization field, the gradient defect interface effectively promotes the separation and transport of photogenerated carriers. Within the pH range of 3.0–11.0, the degradation efficiency increases with increasing pH, and the alkaline environment further enhances the degradation effect. This invention's catalysis can counteract the coexisting anion (Cl...). ‑ CO3 2‑ SO4 2‑ NO3 ‑ ).

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic environmental purification technology, specifically relating to a Zn-doped BiOCl catalyst with a gradient defect interface and its application in the catalytic degradation of antibiotics under the synergistic effect of light field and built-in electric field. Background Technology

[0002] In recent years, with the rapid development of the pharmaceutical, livestock, and medical industries, the large-scale production and widespread use of antibiotics have led to increasingly serious problems with their residues in aquatic environments. Tetracyclines (such as tetracycline hydrochloride) and fluoroquinolones (such as ciprofloxacin), as typical broad-spectrum antibiotics, have been frequently detected in surface water, groundwater, and even drinking water in many parts of the world. Antibiotic residues not only pose a potential threat to aquatic ecosystems but also induce the generation and spread of antibiotic resistance genes in bacteria, posing long-term risks to public health. Traditional treatment methods, such as activated sludge processes, membrane separation technologies, and activated carbon adsorption, can remove antibiotics from water to a certain extent, but they generally have limitations such as incomplete degradation, easy generation of secondary pollution, high energy consumption, or only achieving phase transfer rather than true mineralization. Photocatalysis technology utilizes semiconductor materials to generate highly oxidizing active species under light irradiation, which can deeply mineralize organic pollutants into CO2 and H2O at normal temperature and pressure. Due to its clean, efficient, and sustainable advantages, it is considered one of the ideal strategies for treating trace amounts of recalcitrant organic pollutants in water.

[0003] However, the core of photocatalytic reactions is constrained by the fact that carrier separation, charge transfer, and the generation of reactive oxygen species on the catalyst surface all occur at the solid-liquid interface. Therefore, the degree of matching between the interfacial microstructure, such as defect type, defect concentration, spatial distribution, and the local physical field and chemical environment, directly determines the catalytic efficiency and selectivity. A real photocatalytic system is a typical multi-field coupled environment.

[0004] The reaction process involves the combined action of at least the following physical and chemical fields: (1) the illumination field formed by electron-hole pairs generated by photoexcitation; (2) the built-in electric field generated by lattice distortion, interface polarization, and accumulation of defect charges; and (3) the chemical field composed of solution pH, coexisting anions and cations and their concentrations, and the dissociation morphology of the target pollutant. These "fields" do not exist in isolation, but rather superimpose, cooperate, or antagonize each other on the defect interface at the nanoscale, jointly determining the kinetics and thermodynamic pathway of the catalytic reaction. However, most current domestic and international research focuses on the optimization of single elements, such as single metal doping to regulate band structure and the introduction of single-type defects (such as oxygen vacancies). There is a lack of systematic research on common scientific questions such as "how ion size differences induce gradient defect interfaces" and "how illumination field-built-in electric field-multiple chemical fields (pH, anions) cooperate to regulate the catalytic behavior of defect sites". Especially when designing visible light responsive catalysts, whether multi-field coupling can be used to break through the activity bottleneck remains to be elucidated.

[0005] Bismuth oxychloride (BiOCl), as a typical layered bismuth-based photocatalyst, provides an ideal platform for studying the aforementioned multi-field coupling interface problems due to its unique layered structure and indirect bandgap characteristics. However, its wide bandgap (approximately 3.2-3.5 eV) leads to poor visible light response, and photogenerated electron-hole pairs readily recombine. Metal ion doping and surface defects (oxygen vacancies, metallic BiO2, etc.) further contribute to this problem. 0 The introduction of doping is a common method to improve the visible light response of catalytic catalysts. However, achieving precise synergistic control of doping and defects, especially utilizing the directional construction of interfaces with concentration gradients based on ion size differences, and maximizing catalytic efficiency through multi-field coupling of light field, internal electric field, and chemical environment, remains a challenge in this field. Existing metal ion doping and oxygen vacancy control can extend light absorption to some extent, but they have failed to achieve precise synergistic construction of dopants and gradient defects, nor have they fully explored the catalytic potential under multi-field coupling conditions. Therefore, developing a novel BiOCl-based catalyst capable of simultaneously constructing gradient defect interfaces and operating efficiently and stably under multi-field coupling is crucial for advancing its practical applications. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of existing BiOCl materials, such as poor visible light response, easy recombination of photogenerated carriers, unclear synergistic regulation mechanism of doping and defects, and lack of systematic research on interfacial catalytic behavior under multi-field coupling conditions. This invention provides a gradient defect interface BiOCl material with a wide light absorption range, high carrier separation efficiency, and significant degradation activity under the synergistic effect of light field and built-in electric field, as well as its preparation method and application.

[0007] Technical solution

[0008] A Zn-doped BiOCl material with a gradient defect interface, characterized by: utilizing Zn with a small ionic radius. 2+ (Approximately 0.074 nm) Partially replaces Bi 3+ (Approximately 0.103 nm) induces lattice distortion, constructing "Zn" in BiOCl. 2+ Doping site → Oxygen vacancy → Elemental bismuth (Bi) 0 The gradient defect interface.

[0009] Preferred option: Zn 2+ with Bi 3+ The molar ratio is 1%-10%, preferably 3%.

[0010] The preparation method of the above material involves controlling the amount of zinc acetate doping. Specific steps are detailed in the preparation method section.

[0011] This invention provides a method for preparing the Zn-doped BiOCl material with a gradient defect interface, which is prepared in one step by a solvothermal method by mixing a bismuth source, a chlorine source, a zinc source and propylene glycol.

[0012] Preparation method, specific steps:

[0013] (1) Dissolve the bismuth source in propylene glycol and stir for 20-40 min at a speed of 200-600 r / min to obtain a uniformly dispersed solution A; the bismuth source is selected from one or more of bismuth pentahydrate, bismuth oxide, and bismuth chloride, preferably bismuth pentahydrate.

[0014] (2) Dissolve the chlorine source in propylene glycol and stir to obtain solution B; the chlorine source is selected from one or more of potassium chloride, sodium chloride, and hexadecyltrimethylammonium chloride, preferably potassium chloride.

[0015] (3) Dissolve the zinc source in propylene glycol and stir to obtain solution C; the zinc source is selected from one or more of zinc acetate, zinc nitrate and zinc chloride, preferably zinc acetate.

[0016] (4) While stirring continuously, add solutions B and C to solution A in sequence, and continue stirring for 20-40 min to obtain the precursor mixture;

[0017] In the above steps, the optimal stirring time is 30 min, and the stirring speed is 200-600 r / min, preferably 500 r / min.

[0018] The amount of bismuth source added is based on a final molar ratio of bismuth to chlorine of 1:1. When bismuth chloride is used as the bismuth source, chlorine is included in the chlorine source calculation.

[0019] The amount of zinc source added is based on Zn 2+ with Bi3+ The molar ratio is 1%-10%, preferably 3%.

[0020] (5) Transfer the precursor mixture obtained in step (4) to a high-pressure reactor lined with polytetrafluoroethylene for solvothermal reaction; the solvothermal reaction temperature is 140-220°C. The temperature was set at ℃, and the reaction time was 8-15 h; the heating rate was controlled at 0.5-3 ℃. ℃·min -1 The cooling rate is controlled at 1-3℃·min. -1 The preferred reaction temperature and reaction time are 160°C and 160°C respectively. ℃ and 12 h, with a preferred heating rate of 1 ℃·min -1 The preferred cooling rate is 2 ℃·min -1 .

[0021] (6) After the reaction is complete, cool to room temperature, discard the supernatant, and keep the precipitate. Wash the precipitate several times with a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of (4-24):(1-6), then centrifuge to collect the centrifuged material; dry the centrifuged material to obtain the Zn-doped BiOCl material with a gradient defect interface. Centrifugation is performed at a speed of 5000-8000 r / min, preferably 7500 r / min, and drying is performed at 50-80 °C. The optimal drying temperature and drying time are 60℃ for 8-15 hours. ℃ and 12 h.

[0022] The application of the catalyst obtained in this invention in the photocatalytic degradation of antibiotics. The catalyst is dispersed in an aqueous antibiotic solution, stirred in the dark until adsorption-desorption equilibrium is reached, and then a 300 W xenon lamp (equipped with a 420 nm cutoff filter, λ > 420 nm) is turned on as a visible light source for photocatalytic degradation. The pH range of the antibiotic aqueous solution can be 3-11, with higher degradation efficiency under alkaline conditions; a pH range of 7-11 is preferred. Additionally, the above-mentioned antibiotic aqueous solution may also contain Cl. - CO3 2- SO4 2- and NO3 - One or more of them.

[0023] Beneficial effects

[0024] (1) The gradient defect interface can be constructed in one step by the "ion size difference driven" strategy. The method is simple and controllable, and the yield is as high as 94.80%.

[0025] (2) The light absorption edge is red-shifted to the visible light region, the band gap is reduced to 2.86 eV, and the visible light absorption capacity is significantly improved.

[0026] (3) The gradient defect interface and the built-in polarization field work together to suppress carrier recombination and effectively enhance the generation of reactive oxygen species.

[0027] (4) The apparent degradation efficiency of tetracycline and ciprofloxacin under visible light was increased by 1.29 times and 1.83 times respectively compared with pure BiOCl, and it maintained excellent catalytic stability in the full pH range (3.0-11.0) and in the environment of multiple coexisting anions.

[0028] (5) The synergistic mechanism of photocatalytic performance enhancement by multi-field coupling of light field, built-in electric field and pH was initially revealed, providing a new strategy for the design of high-performance catalysts in complex water environments. Attached Figure Description

[0029] Figure 1 The surface defect distribution of the catalysts obtained in Comparative Example 1 and Examples 1-3 shows that the oxygen vacancy concentration gradually increases with the increase of Zn doping amount.

[0030] Figure 2 The X-ray diffraction patterns of the catalysts obtained in Comparative Example 1 and Examples 1-3 show that Zn doping leads to surface metallic bismuth (Bi). 0 Further extraction; Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1: Preparation of 3%-Zn-BOC 1) Weigh 5 mmol of bismuth nitrate pentahydrate and dissolve it in 30 mL of propylene glycol. Stir at 500 r / min for 30 min to obtain a uniformly dispersed solution A.

[0033] (2) Weigh 5 mmol of potassium chloride and dissolve it in 20 mL of propylene glycol. Stir under the same conditions to obtain solution B.

[0034] (3) Weigh 0.15 mmol of zinc acetate (Zn 2+ with Bi 3+ Dissolve (at a molar ratio of 3%) in 10 mL of propylene glycol to obtain solution C;

[0035] (4) Under continuous stirring at 500 r / min, add solutions B and C to solution A in sequence, and continue stirring for 30 min to obtain a precursor mixture;

[0036] (5) Transfer the precursor mixture to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, and then... ℃·min -1 The temperature was increased to 160℃ at a rate of [missing information], and the solvothermal reaction was carried out for 12 h; after the reaction was completed, the temperature was increased at 2℃·min [missing information]. -1 The temperature drops to room temperature at a rate that allows it to cool down.

[0037] (6) Discard the supernatant and keep the precipitate. Wash the precipitate with a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of 4:1, centrifuge at 7500 r / min, and repeat the washing-centrifugation operation 5 times; dry the centrifuged material at 60℃ for 12 h, grind it into a fine powder, and you will get 3%-Zn-doped BiOCl material, denoted as 3%-Zn-BOC, with a yield of about 95%.

[0038] Example 2: Preparation of 1%-Zn-doped BiOCl (1%-Zn-BOC)

[0039] Adjust the amount of zinc acetate used in step (3) to 0.05 mmol (Zn 2+ with Bi 3+ (The molar ratio is 1%), and the remaining steps are the same as in Example 1, thus obtaining 1%-Zn-BOC.

[0040] Example 3: Preparation of 5%-Zn-BOC

[0041] Adjust the amount of zinc acetate used in step (3) to 0.25 mmol (Zn 2+ with Bi 3+ (The molar ratio is 5%), and the remaining steps are the same as in Example 1, thus obtaining 5%-Zn-BOC.

[0042] Comparative Example 1: Preparation of pure BiOCl (BOC)

[0043] Without adding zinc acetate, i.e. omitting step (3), and without introducing solution C, the remaining steps are the same as in Example 1, thus obtaining pure BiOCl material, denoted as BOC.

[0044] Application Example 1: Visible light-catalyzed degradation of tetracycline (TC)

[0045] Weigh 20.0 mg of the catalysts prepared in Examples 1-3 and Comparative Example 1, respectively, and disperse them in 100 mL of a solution with a concentration of 1.0 × 10⁻⁶. -5 mol·L -1The tetracycline hydrochloride solution was used. After stirring in the dark for 30 min to reach adsorption-desorption equilibrium, a 300 W xenon lamp (equipped with a 420 nm cutoff filter, λ > 420 nm) was turned on as the visible light source. Samples were taken every 20 min, filtered through a 0.22 μm filter membrane, and the TC concentration was measured using a UV-Vis spectrophotometer. After 100 min of visible light irradiation, the degradation rates of TC by BOC, 1%-Zn-BOC, 3%-Zn-BOC, and 5%-Zn-BOC were 70.65%, 90.62%, 91.78%, and 90.74%, respectively. Among them, 3%-Zn-BOC showed the best degradation activity.

[0046] Application Example 2: Visible light photocatalytic degradation of ciprofloxacin (CIP)

[0047] The TC solution in Application Example 1 was replaced with an aqueous solution of ciprofloxacin of the same concentration, while all other operating conditions remained the same. After 100 min of visible light irradiation, the degradation rates of CIP by BOC, 1%-Zn-BOC, 3%-Zn-BOC, and 5%-Zn-BOC were 28.08%, 39.22%, 51.58%, and 30.45%, respectively. The apparent degradation efficiency of 3%-Zn-BOC was approximately 1.84 times higher than that of pure BOC, indicating that the gradient defect interface has a significant catalytic enhancement effect on antibiotics with different structures.

[0048] Application Example 3: Effect of different initial pH values ​​on TC degradation performance

[0049] Using 3% Zn-BOC as a catalyst, with 0.1 mol·L⁻¹ -1 The initial pH of the TC solution was adjusted to 3.0, 5.0, 7.0, 9.0, and 11.0 using HCl or NaOH, with other conditions remaining the same as in Application Example 1. The results showed that within the pH range of 3.0–11.0, the TC degradation efficiency of both BOC and 3%-Zn-BOC increased with increasing pH. After 100 min of visible light irradiation, the degradation efficiency of BOC gradually increased from 63.31% at pH 3.0 to 72.38% at pH 11.0; the degradation efficiency of 3%-Zn-BOC increased from 86.18% at pH 3.0 to 94.80% at pH 11.0. These results indicate that an alkaline environment is beneficial for enhancing photocatalytic degradation efficiency, and that 3%-Zn-BOC maintains significantly better catalytic activity than pure BOC under different pH conditions, demonstrating the synergistic enhancement effect and adaptability of the gradient defect interface in different chemical environments.

[0050] Application Example 4: The Effect of Coexisting Anions on Degradation Performance

[0051] Using 3% Zn-BOC and BOC as catalysts, 5 mmol·L⁻¹ was added to the TC reaction system of Application Example 1, respectively. -1 Sodium chloride, sodium carbonate, sodium sulfate, and sodium nitrate are used to introduce Cl. - CO3 2- SO4 2- and NO3 - Coexisting anions were investigated to examine the influence of common inorganic salts in actual water bodies on the photocatalytic degradation process.

[0052] The results showed that in NaCl solution, both BOC and 3%-Zn-BOC exhibited significant inhibitory effects. In Na2CO3 and Na2SO4 solutions, BOC showed a slight inhibitory effect, while the degradation effect of 3%-Zn-BOC was almost unaffected. In NaNO3 solution, nitrate had no significant effect on either catalyst. (Addition of CO3...) 2- Afterwards (possibly due to increased alkalinity), 3%-Zn-BOC achieved a TC degradation rate of 91.91% within 100 min, comparable to that without the addition of anions, and with a faster degradation rate.

[0053] Multi-field synergistic catalytic degradation performance

[0054] Coupling of illumination field and built-in polarization field: Zn 2+ Doping and OVs work together to regulate the band structure, forming defect energy levels, redshifting the light absorption edge to the visible light region, enhancing the built-in electric field, and effectively promoting electron-hole separation.

[0055] Coupling of Irradiation Field and pH Chemical Field: The changes in TC degradation efficiency within the pH range of 3.0–11.0 were systematically investigated. The results showed that pH significantly affected the photocatalytic degradation of both BOC and 3%-Zn-BOC systems. The degradation rate was higher in alkaline media, indicating a stronger tendency for TC photolysis in alkaline solutions. After 100 min of visible light irradiation, as the pH increased from 3.0 to 11.0, the degradation efficiency of BOC increased from 63.31% to 72.38%, while the degradation efficiency of 3%-Zn-BOC further increased from 86.18% to 94.80%. This trend reveals that an alkaline environment favors the conversion of photogenerated holes into hydroxyl radicals or direct oxidation, while also influencing the surface charge of the catalyst and the dissociation morphology of TC molecules, thereby enhancing degradation. 3%-Zn-BOC maintained a significant advantage across the entire pH range, demonstrating the synergistic enhancement effect of the gradient defect interface under different chemical environments.

[0056] Effect of coexisting anions: Introducing Cl... - CO3 2- SO4 2- and NO3 -The effect of anionic chemical fields on the photodegradation process was investigated. The results showed that in the systems where the above examples coexisted, the degradation rate of TC was inhibited to some extent by the BOC catalyst; while 3%-Zn-BOC had no significant effect on the degradation efficiency of this antibiotic and could be applied to practical systems containing Cl. - CO3 2- SO4 2- and NO3 - Antibiotic wastewater.

[0057] Table 1. Comparison of the tetracycline degradation performance of the catalysts described in Examples 1-3 and Comparative Example 1 as described in Application Example 1.

[0058] Catalyst 0 min 20 min 40 min 60 min 80 min 100 min BOC 0.00 50.35 63.99 69.48 70.31 70.65 BOC-Zn-1% 0.00 68.52 79.35 87.05 89.64 90.62 3%-Zn-BOC 0.00 75.39 87.21 90.24 91.01 91.78 5%-Zn-BOC 0.00 61.46 76.2 85.70 89.27 90.74

[0059] Table 2. Comparison of the degradation performance of ciprofloxacin by the catalysts described in Examples 1-3 and Comparative Example 1 as described in Application Example 1.

[0060] Catalyst 0 min 20 min 40 min 60 min 80 min 100 min BOC 0.00 18.07 21.55 22.04 24.61 28.08 BOC-Zn-1% 0.00 34.03 35.03 35.25 38.34 39.22 3%-Zn-BOC 0.00 45.66 46.84 49.68 50.46 51.58 5%-Zn-BOC 0.00 21.61 26.36 26.97 29.70 30.45

[0061] Table 3. Comparison of tetracycline degradation performance of the catalyst described in Comparative Example 1 under various anion coexistence conditions.

[0062] BOC 0 min 20 min 40 min 60 min 80 min 100 min <![CDATA[Cl - ]]> 0.00 48.51 56.51 58.09 59.32 58.99 <![CDATA[CO3 2- ]]> 0.00 58.99 61.12 61.79 62.46 63.1 <![CDATA[SO4 2- ]]> 0.00 43.33 56.92 62.22 64.91 64.02 <![CDATA[NO3 - ]]> 0.00 46.69 59.77 67.19 69.14 70.2

[0063] Table 4. Comparison of tetracycline degradation performance of the catalyst described in Example 2 of Application Example 1 under various anion coexistence conditions.

[0064] 3%-Zn-BOC 0 min 20 min 40 min 60 min 80 min 100 min Cl⁻ 0.00 86.28 86.89 86.93 86.5 86.42 <![CDATA[CO3 2- ]]> 0.00 90.6 90.41 91.49 90.89 91.91 <![CDATA[SO4 2- ]]> 0.00 71.61 84.26 88.59 89.13 90.24 <![CDATA[NO3 - ]]> 0.00 73.72 85.32 88.78 90.83 89.47

[0065] Table 5. Comparison of tetracycline degradation performance of the catalyst described in Comparative Example 1 under different acid and alkaline conditions.

[0066] BOC 0 min 20 min 40 min 60 min 80 min 100 min pH = 3 0.00 42.27 56.1 60.75 62.78 63.31 pH = 5 0.00 57.22 63.36 64.82 65.8 66.22 pH = 7 0.00 41.4 57.9 61.76 62.72 63.18 pH = 9 0.00 54.75 65.83 68.27 69.45 70.83 pH = 11 0.00 64.4 68.66 70.54 71.44 72.38

[0067] Table 6. Comparison of tetracycline degradation performance of the catalyst described in Example 2 of Application Example 1 under different acid and alkaline conditions.

[0068] 3%-Zn-BOC 0 min 20 min 40 min 60 min 80 min 100 min pH = 3 0.00 72.92 80.78 83.16 84.68 86.18 pH = 5 0.00 82.68 85.12 85.06 86.15 86.82 pH = 7 0.00 89 92.37 93.82 94.5 94.72 pH = 9 0.00 87.12 89.2 90.41 92.25 93.07 [[ID= 0.00 88.56 91.68 93.94 95.45 94.80

[0069] .

Claims

1. A Zn-doped BiOCl material with a gradient defect interface, characterized in that: Utilizing Zn with its small ionic radius 2+ Partially replaces Bi 3+ Inducing lattice distortion, Zn was constructed in BiOCl. 2+ Doping site → Oxygen vacancy (OVs) → Elemental bismuth (Bi) 0 The gradient defect interface.

2. The Zn-doped BiOCl material with a gradient defect interface according to claim 1, characterized in that: Zn 2+ with Bi 3+ The molar ratio is 1%-10%, preferably 3%.

3. A method for preparing a Zn-doped BiOCl material with a gradient defect interface as described in claim 1 or 2, characterized in that, The bismuth source, chlorine source, zinc source, and propylene glycol were mixed and synthesized in one step using a solvothermal method. The specific steps are as follows: (1) Dissolve the bismuth source in propylene glycol and stir to obtain a uniformly dispersed solution A; (2) Dissolve the chlorine source in propylene glycol and stir to obtain solution B; (3) Dissolve the zinc source in propylene glycol and stir to obtain solution C; (4) While stirring continuously, add solutions B and C to solution A in sequence, and continue stirring to obtain a precursor mixture; (5) Transfer the precursor mixture obtained in step (4) to a high-pressure reactor lined with polytetrafluoroethylene for solvothermal reaction; the solvothermal reaction temperature is 140-220°C. o C, reaction time is 8-15 h; heating rate is controlled at 0.5-3℃·min -1 The cooling rate is controlled at 1-3℃·min. -1 ; (6) After the reaction is completed, cool to room temperature, discard the supernatant and keep the precipitate; wash the precipitate several times with a mixed solvent of deionized water and anhydrous ethanol in a volume ratio of (4-24): (1-6), then centrifuge and collect the centrifuged material; dry the centrifuged material to obtain the Zn-doped BiOCl material with gradient defect interface.

4. The method according to claim 3, characterized in that, The bismuth source in step (1) is selected from one or more of bismuth nitrate pentahydrate, bismuth oxide, and bismuth chloride, preferably bismuth nitrate pentahydrate; the chlorine source in step (2) is selected from one or more of potassium chloride, sodium chloride, and hexadecyltrimethylammonium chloride, preferably potassium chloride; the zinc source in step (3) is selected from one or more of zinc acetate, zinc nitrate, and zinc chloride, preferably zinc acetate.

5. The method according to claim 3, characterized in that, Step (4) The amount of bismuth source added is based on a final molar ratio of bismuth to chlorine of 1:1; when bismuth chloride is used as the bismuth source, chlorine is included in the chlorine source; the amount of zinc source added is based on Zn 2+ with Bi 3+ The molar ratio is 1%-10%, preferably 3%.

6. The method according to claim 3, characterized in that, In steps (1) to (4), the stirring rate is 200-600 r / min, preferably 500 r / min; in step (6), the centrifugation is performed at a speed of 5000-8000 r / min, preferably 7500 r / min, and the drying is performed at 50-80℃ for 8-15 h. The optimal drying temperature and drying time are 60℃ and 12h, respectively.

7. The method according to claim 3, characterized in that, In step (5), the reaction temperature and reaction time are 160℃ and 12 h, respectively, with a preferred heating rate of 1℃·min. -1 The preferred cooling rate is 2℃·min. -1 .

8. The application of the catalyst according to claim 1 or 2, in the photodegradation of antibiotics.

9. According to the application described in claim 8, the catalyst is dispersed in an antibiotic aqueous solution, and after stirring in the dark to reach adsorption-desorption equilibrium, a 300 W xenon lamp (equipped with a 420 nm cutoff filter, λ > 420 nm) is turned on as a visible light source for photocatalytic degradation; the pH range of the antibiotic aqueous solution can be 3-11, and the degradation efficiency is increased under alkaline conditions, preferably a pH range of 7-11.

10. The application according to claim 8 or 9, wherein the aqueous antibiotic solution further contains Cl. - CO3 2- SO4 2- and NO3 - One or more of them.

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